Question: The physical quantity of a millimetre is represented by the symbol L. Which is it?
Paraphrase: The symbol L represents the physical quantity of a millimetre. Which one is that?
SPARQL (Wikidata): SELECT ?answer WHERE { wd:Q174789 wdt:P111 ?answer . ?answer wdt:P416 ?x FILTER(contains(?x , 'L'))}
Answer: length